STREPTOCOCCUS INFECTIONS
STEPHANIE SPECK
Bundeswehr Institute of Microbiology, Department of Virology and Rickettsiology, Munich, Germany
Streptococci are pyogenic bacteria of the family Strepto- coccaceae, genus Streptococcus, and are commonly associated with suppurative infections and abscess formation.
Streptococci are Gram- positive cocci less than 2 μm in diameter that occur in pairs or chains of varying lengths. Most streptococci are facultatively anaerobic, catalasenegative, non-spore-forming and non-motile. Most of the streptococci of veterinary importance occur worldwide as commensals of the upper respiratory and lower urogenital tract. Pyogenic streptococci cause mastitis in cattle and other hosts, equine strangles, meningoencephalitis, arthritis and cervical lymphadenitis in swine, neonatal septicaemia in kittens and lymphadenitis in juvenile cats and laboratory rodents. Some of the streptococci of veterinary importance are Streptococcus agalactiae, S. canis, S. dysga- lactiae (subsp. dysgalactiae, equisimilis), S. equi (subsp. equi, ruminatorum, Zooepidemicui), S. gallolyticus subsp. gallolyticus, S. halichoeri, S. iniae, S. marimammalium, S. phocae, S. pneumoniae, and S. suii.The broad host range and diversity of tissue tropism of veterinary pathogenic streptococci suggest multiple paths in the evolution of this bacterial genus. The genus comprises highly host-adapted pathogens (e.g. S. equi subsp. equi) uniquely fitted for invasion of specific host tissues (e.g. S. agalactiae) but also includes pathogens with almost no host adaptation (e.g. S. equi subsp. Zooepidemicui, S. dysgalactiae subsp. equisimilis) and capable of causing disease only as opportunists concurrent with pre-existing tissue damage or impaired immune functions1-30). Streptococci are susceptible to desiccation and do not survive for
TABLE 37.1 Types of Staphylococcus disease and associated lesions in free-ranging animals in Europe.
| Host | Staphylococcus species | Disease condition/carrier (C) status | Gross and microscopic IesionsZabnormal blood test results | Geographic origin of the report | Reference |
| Red squirrel (Sciurus vulgaris) | S. aureusy ST49#, c+* S. aureus, ST49#, c+ | Scabs on nose, lips, digits; ischaemic necrosis of digits, swollen lip covered by dried exudate, inflamed swelling of the eyelid Respiratory distress | Exudative, ulcerative and necrotic dermatitis, epidermal hyperplasia and hyperkeratosis Inflamed nasopharyngeal and laryngeal mucosa with whitish, plaque-²²êå lesions; tongue and nasopharynx with mucosal ulceration and necrosis; lungs congested with localized areas of consolidation and marginal emphysema; inhalation pneumonia secondary to laryngeal ulceration and necrosis | UK UK | 20 21 |
| Red squirrel | 5, aureus S. scuiri | Bacterial infections secondary in most squirrel pox cases contributing to the dermatitis lesions; both 5. aureus and 5. scuiri may cause septicaemia in squirrel pox cases | Pyogranulomatous SuppurativeZexudative infections of the skin | UK | 22 |
| Mountain hare (Lepus timidus) | S. aureus, c+ | Secondary bacterial infection in contagious muco-cutaneous dermatitis | Pyogranulomatous, suppurative infection of the skin | Finland | 23 |
| Chaffinch (Fringilla coelebs) | S. aureus, c+ | Tassle-Hke foot lesions | Lesions (not specified) in multiple organs suggestive of 5. aureus septicaemia | UK | 24 |
| Mountain hare | S. xylosus, c~; S. warneri, c~ | Secondary bacterial infection in contagious mucocutaneous dermatitis | Pyogranulomatous, suppurative infection of the skin | Finland | 23 |
| European brown hare (Lepus europaeus) | S. species | Pyogenic skin infection, subcutaneous abscesses | Abscessating lesions in internal organs, septicaemia | Germany | 25 |
| Spanish ibex (Capra pyrenaica hispanicd) | 5. aureus, c+; S. xylosus, c~; S. epidermidis, c~ | C (nares, conjunctiva, vagina) | - | Spain | 26 |
| European bison (Bison bonasus bonasus} | S. aureus c+, S. epidermidis, S. capitis, S. chromogenes, S. ho minis, S. Ientus, S. sciuri, S. warneri, S. xylosus, c~ | C (normal vaginal microflora) | Poland | 27 | |
| Bank vole (Clethrionomys | S. Stepanovicii sp. nov., c- | C (skin, fur, intestinal tract) | - | Poland | 19 |
glareolus), root vole (Microtus oeconomus), field mouse (Apodemus agrarius)> common shrew (Sorex araneus}> lesser shrew (5. minutus)
c+ — coagulase-positive; c - coagulase-negative, C - carrier status, # — sequence type (ST) 49 according to the multilocus sequence typing (MLST) database
long periods outside the animal host.
Streptococcus is transmitted by direct contact, mastitic milk, pus, nasal discharge, or feed or water directly contaminated by a shedding animal. The occurrence of Streptococcus spp. in free- ranging and captive wild animals is summarized in Table 37.2.Virulence of the pathogenic streptococci is based on surface structures that directly or indirectly impede phagocytosis, for example due to binding of host plasma proteins or fibrinogen. The hyaluronic acid capsule and the antiphagocytic cell wall M- proteins are the best- known streptococcal virulence factors. Other factors include streptolysin S and O, a hyaluronidase, proteases, streptokinase, neuraminidases and leucocidal toxins(30).
Clinical signs of Streptococcus infection are non-specific. Types of disease and pathologic changes in free-ranging and captive wildlife are given in Table 37.2.
Specimens for isolation of the organism depend on the disease condition and may include nasal discharge, pus, mastitic milk and affected tissue. As streptococci are susceptible to desiccation, swabs should be placed in transport medium. Direct microscopy of Gram-stained smears may show Gram-positive cocci in the typical chain formation; pneumococci (S. pneumoniae) occur as pairs of bacteria. Streptococci can be grown on blood agar, selective blood agar and MacConkey agar. Inoculated plates are incubated aerobically at 37°C for 24—48 hours. Colony appearance, haemolysis, biochemical reactions and other characteristics (e.g. CAMP test) are used to identify Streptococcus species. The majority of pathogenic streptococci possess a dominant serologically active cell wall antigen used as the basis of the Lancefield grouping system for streptococcal identification. These group-specific antigens (A—H and K-V) are used in a variety of methods for sero- grouping an unknown isolate. The pyogenic animal streptococci belong to groups B, C, D, E, G, L, U and V(30).
TABLE 37.1 Occurrence of Streptococcus in free-ranging wildlife in Europe.
| Host(s) | Streptococcu species | Disease condition/carrier status (C) | Gross and microscopic lesions | Geographic origin of the report | Reference |
| Roe deer (Capreolus capreolus) | S. gallolyticu( subsp. gallolyticus | Weakness | Subcutaneous oedema, multiple petechiae and ecchymotic haemorrhages incl. pulmonary artery, aortic valve, endocardium; cardiac vasculitis | Spain | 31 |
| Red fox (Vulpes vulpes) | Streptococcu sp., group G | Subcutaneous purulent lesions around bite wounds | Septicaemia, toxaemia secondary to penetrating bites | UK | 32 |
| Eurasian river otter (Lutra lutra) | S. dysgalactiae | Bite wounds, abscess, isolated from lung | Severe subcutaneous infection | UK | 33, 34 |
| Harbour seal (Phoca | S. equi subsp. | Secondary infection concurrent | Associated lesions not | German North | 35 |
| vitulina) | zooepidemicus | to phocine distemper outbreak; isolated from lung, liver, spleen, kidney, intestine, vaginal swab | described | Sea | |
| Caspian seal (Phoca caspica), harbour seal, grey seal (Halichoerus grypus) | S.phocae | Secondary infection concurrent to phocine distemper outbreak; isolated from lung, liver, spleen, heart, cerebrum | Associated lesions not described | Caspian Sea, German North and Baltic Sea | 36, 37 |
| Grey seal | S.phocae | Bite wound | Septic arthritis | UK | 38 |
| Grey seal, habour seal | S. marimammalium | Isolated from lung | Associated lesions not described | UK | 39 |
| Grey seal | S. halichoeri | C | Associated lesions not described | UK | 40 |
| Spanish ibex (Capra pyrenaica hispanica) | S. equi subsp. zooepidemicus | C; isolated from nasal and vaginal swabs | Associated lesions not described | Spain | 26 |